Hydraulic rate control piston-type devices are used in a wide variety of applications to support a component from a structural member and control the pivotal movement of the component. For example, hydraulic rate control piston-type devices are commonly used oil commercial passenger aircraft to support and control the opening rate of pivoting type overhead stowage bins. U.S. Pat. No. 6,874,731 discloses a modular overhead stowage bin system for an aircraft passenger cabin. In a wide body, multi-aisle aircraft, the overhead stowage bins include outboard stowage bins positioned above the right and left side seats of the aircraft and inboard stowage bins positioned above the center seats. The overhead stowage bin compartments are readily accessible to passengers to open the bins to stow and remove carry-on luggage, packages, coats and the like when standing in the passenger aisles. As illustrated in the aforenoted patent, each of the pivoting type overhead stowage bin buckets is mounted for pivotal movement in the bin structure. The pivot bin bucket is supported by one or more hydraulic rate control piston-type devices that controls the opening rate of the bin bucket in the bin structure.
In conventional stowage bin systems, each piston-type device connects to and extends between a mounting lug coupled to the stowage bin bucket it supports and a mounting lug coupled to the bin structure. The typical piston-type device includes a hydraulic cylinder with a piston head and piston rod. The piston head is mounted to a proximal end of the piston rod and an eye socket is mounted to a distal end of the piston rod for securing the distal end of the piston rod to the stowage bin bucket. The piston head is disposed within the housing of the cylinder for movement along the axis of the cylinder housing. The interior of the cylinder housing is filled with a hydraulic fluid. A second eye socket is mounted to the distal end of the cylinder housing for securing the piston device to the bin structure. The piston rod extends through the proximal end of the cylinder housing. Conventional hydraulic rate control devices associated with stowage bins typically cause the stowage bin to open slowly when the bin is empty, but to open faster when the bin is fully loaded.
U.S. Pat. No. 3,999,745 discloses a hydraulic rate control piston-type device for use in connection with an overhead storage bin in the passenger cabin of a commercial aircraft. The disclosed device incorporates a compression rate control valve that includes a spring-biased, inversely-tapered pin valve element disposed within a piston head mounted on the piston rod. The high side pressure acts upon the forward face of the valve element in opposition to the bias force imposed upon the rearward face of the valve element to vary the flow area of an annular orifice opening in the forward face of the piston head through which hydraulic fluid passes from the high pressure side to the low pressure side of the piston head during the compression stroke. The flow area provided by the orifice varies directly in response to the fluid pressure on the high pressure side of the piston head in inverse relationship thereto to regulate the flow of fluid therethrough as a means of controlling the rate of collapse of the piston rod device under a compression stroke imposed on the piston rod during movement of the overhead storage bin bucket in a commercial aircraft. In the disclosed piston device, a variable orifice valve having a spring-biased, tapered valve pin is attached to the head of the piston rod. As the piston head translates in compression under an applied load within the hydraulic cylinder of the device under application of a compressive load, hydraulic fluid is metered through the valve from one side of the piston head to the other side of the piston head. The hydraulic fluid passes from the high pressure side of the cylinder through a variable flow area orifice at the face of the valve into an interior valve chamber and thence therefrom through a fixed flow area into the low pressure side of the interior of the cylinder. It is stated that the valve produces a snubbing (retarding) force by restricting the flow of fluid through the variable orifice, the flow area of which is said to vary in inverse proportion to the load applied. However, since the spring biasing the tapered pin within the orifice opening in the face of the valve must have a high enough spring rate to work effectively at the higher applied loads, control of fluid flow rate through the valve to a near constant rate is not achievable over a wide range of applied loads.
Additionally, Enidine Incorporated, the assignee of this application, manufactures and sells a rate control device of the hydraulic piston-type for use in connection with controlling the opening and closing rate of a door which provides relatively constant flow rate control over a wide range of applied loads, but which has a relatively large diameter. The Enidine device includes a piston rod having a piston head disposed within a closed hydraulic cylinder filled with a hydraulic fluid. The piston rod translates outwardly along the longitudinal axis under a tensile load when the device extends as a person closes the door. The piston rod translates inwardly along the longitudinal axis under a compression load when the device collapses as a person opens the door.
This Enidine device includes a pair of Flosert® flow rate control valves, manufactured and distributed by The Lee Company, Westport, Conn., mounted in the piston head diametrically opposite each other and radially outward of the coaxial longitudinal axis along which the piston rod translates within the cylindrical housing of the piston device. One of the rate control valves is arranged to control the rate of fluid flow therethrough during the compression stroke of the device, while the other of the rate control valves is arranged to control the rate of fluid flow therethrough during the tension stroke of the device. Each flow rate control valve includes an interior chamber having a variable flow area orifice opening to the interior of the cylinder on one side of the piston head and a fixed flow area orifice opening to the interior of the cylinder on the other side of the piston head. A spring-biased valve member within the interior chamber of the valve translates axially in response to the force of the pressure differential between an intermediate pressure within the interior chamber of the valve and the low-side pressure acting against the opposing spring bias force to vary the flow area of the variable flow area orifice as the high side pressure increases or decreases under a load applied to the piston rod. As a result of the varying flow area between the high side pressure chamber of the cylinder and the subchamber of the valve, the intermediate pressure within the subchamber remains relatively constant as the high side pressure increases or decreases. As the valve member responds to the intermediate pressure acting thereon, a relatively constant flow rate control may be realized over a wider load range. However, given the radially outward positioning of the flow control valves, a relatively large diameter cylindrical housing is required which increases both the size and weight of this rate control device.